The present invention relates to a production control apparatus and method for effectively producing one type or a plurality of types of products from a material.
A CAM (computer aided manufacturing) or CIM (Computer Integrated Manufacturing) system is directed to making a production through the utilization of a computer and its main function is to perform production control.
As such production procedure, there are known various kinds of procedures. For a multi-product assembly line for producing many types of products as in the production of semiconductor devices, it is essential to control their production ratio. As such a control method, a procedure is designed for leveling the production pace.
The production ratio control method as disclosed, for example, in JPN PAT APPLN KOKAI PUBLICATION NOs. 64-34644 and 6-328351 is directed to controlling the production ratio of types of products by dynamically updating predetermined sequence data.
Further, the method as disclosed in JPN PAT APPLN KOKAI PUBLICATION NO. 2-36037 is such that, in order to prevent too many and too few of work (intermediate products, semi-finished products and unfinished products) being waited for a subsequent step or steps--the standby numbers--, the order of executing steps is properly switched from one step to another. And JPN PAT APPLN KOKAI PUBLICATION NO. 3-14675 discloses in-process vehicle management apparatus by which the number of vehicles in process is grasped on the basis of their specific use so as to utilize it for vehicle management.
Further, Menjyu Satoshi "the level adjustment technique for a planned production target" (The Institute of System Control and Information Engineers) in "95 Dissertations of the Production Scheduling Symposium" (Oct. 2, 1995 in Kyoto) pp 187-192 is directed to uniforming daily quantities of processing at respective steps.
Finally, the production ratio control apparatus disclosed in JPN PAT APPLN KOKOKU PUBLICATION NO. 6-328351 is of such a type that, when, with counters arranged relative to corresponding types, a given type of items starts its production process, one counter corresponding to another type of items is incremented by a proper amount so as to progress the production process at a desired ratio.
In the production ratio control apparatus disclosed in JPN PAT APPLN KOKAI PUBLICATION NOs. 64-34644 and 6-328351, the type of items have their production ratio controlled through the updating of the production sequence data and it is, therefore, not suitable to accurately control the quantity of products for each type of their items.
Further, the method and apparatus as disclosed in JPN PAT APPLN KOKAI PUBLICATION NOs. 2-36037 and 3-14675 are directed to grasping/controlling the product inventory or work and is not suitable to control the production ratio and quantity of their types over a given period of time.
In the technique as described in "the leveling adjustment technique for a production target plan", it is possible to level the quantity of processing at each job step but it is not suitable to control the quantity of the work at each step.
In the apparatus as described in JPN PAT APPLN KOKAI PUBLICATION NO. 6-328351, it is possible to control the processing ratio of the respective types of items, that is, their production ratio, and to accurately control the production quantity. However, it is necessary to, at each start of processing, have the values of counters for the other types varied, that is, have the values of these counters varied one less than the number of types involved, so that, the more the types of items, the more counters have to be varied in a substantially proportional relation.